Manufacture of incandescent materials for electric lighting.



. Lighting,

; UNITEI "g PATENT GEORG ALEFELD, -on DARMSTADT,

GERMANY, AssrcNoR rro LUDWIG GANS, OF FRANKF'OR'lfON-THE-MAIN, GERMANY.

MANUFACT'URE QF INCNDESCENT MATERIALS Fll ELECTRIC LIGHTING.

srncmrcazrrcn forming pm of Letters Patent no. 656,017?, aai-ed August 14,

1899.. s'ril Harmonia. nu man.)

. pplloetion flied .Time 15,-

To @ZZ whom, t may concern:

Be itknown that I, GEORGALEFELD, a citizen of Germany, and a resident of Darmstadt, in the Empire of Germany, have invented a new and useful Improvement in the Manufacture of Incandescent Materials for Electric of which the following is aspecification.

It has been long known that certain refrac-v tory bodies-such as, for example, porcelain,

A `magnesia, lime, zirconia,&c.-emit a brilliant lightwhen heated to a sufciently-hightemperature. Since the heatin g eect of the electric current has been known numerous attempts have been made to take advantage of this property and render these bodies available for practical illumination. The production and introduction as a practical illumi- -nant by Auer von Welsbach of bod-ies which become incandescent when heated by a gasilame gave a new impulse to eiorts` in this direction, the more particularly since through his publications the number of known 1uminous earths has been considerably' increased. The rst attempt of this kind which attracted special attention was these-called Jablochkoff lamp; but its practical defects' were found to so outweigh its merit that it soon disappeared from the eld. Walther Nernsthas lately again taken up this idea and has constructed incandescents called, after'his name, the Nernst lamp. With bot-h lthe Jablochkoi-and Nernst lamps the principal difficulty consists in the initial heating of the incandescent body to a sufhcien tlyhigh temperature, an initial step rendered necessary by the factthat all these luminous earths conductV the electric current very poorly at normal temperatures and'only become good conductors after theirtemperature has been considerably raised. Itis therefore necessary first to heat the to-be-incandescent body by a gas-'burner or some other extraneous source of heat or means of heating beforeA it will pass `'the electric current and through its action become incandescent. J ab.- -lochkoi, for example, held his incandescent body between a pair of tongs, the arms of whichtwere connected with the conductingwires of an -electric current, connecting the saidl arms with' the .incandescent by a thin I filament of a carbon-containing material, by which the current first passed. This heated the filament, which in turn heated the'to-beincandescent bodyv until it became itself a conductor and. actually incandescent. The carbon filament was, however, destroyed in thisfoperation and had to be replacedbya Nernst seeks to accomplish this. result by thin platinum wire, thus heating the coil, which in turn heats the to-be-incandescent body sucientlyto enable it to pass the current.when it becomesi-ncandescent and at ically cut out ofthe circuit. A

V'llheobject of my invention is tol accomplish the same ultimateresult in a much more same time dispense with all sources and means of extraneous initial heating not'so united tothe incandescent body as to form over, my initial heating device is not only capable of prolonged repeated use without impairment, but it also dispenses with any form of cutting-out device, since it remains eration.

In the drawings forming part of this specif ication, Figure l represents a perspective View and an axial section of an improved incandescentv in the form of ahollow cylinder. Figs. 2 and 3 are like views and sections of improved incandescents in the form of curved tubes. Fig-4 represents a magnified crosssection through either of said hollow and tubular incandescente, and Fig. 5 represents a perspective view and cross-section of another form. I

Like letters refer to like parts in all the gures. y A

My improved incandescent iscomposed of a suitable body a, cmposed of one or more of those oxids of the earthypmetais which become luminous at elevated temperatures and a film-like partial coating b of one or more of the highly-.infusible metals of the platinum group to constitutea practically-indestructible preliminary conductor,'and it 1s 1n practice used in connection with a suitable elecleading the electric current through a coil ofysimple, eective, and durable way and at thev constantly in circuit while my lamp is in opv new'ilament every time the lamp was used. p

the same time --the heating-.coil is automat- Y practically an integral part thereof.` Moretral gasl-such'as carbonic acid, hydrogen, or

illuminating-gas'-as is well known. If the mixture contains iridium, it is preferable to Sburn it in ina closedmufie filled with hydrogen alone and not with illuminating-gaslin order to revent the formation of iridiuxn carbid,

('Ir.C4.I)) .therefore preferable, jto burn@ in in a closed mu'le in the presence of hydrogen alone, sincethis method is adapted to all lusters. Of course such aceramic luster should be chosen as will after burning vin leave a metallic film of a suiciently-high melting-point not to fuse on the rent.

Generally a single application and ring of the luster gives suliicient thickness; but where the solution or mixture of the luster and firing may be repeated -until tory coating has beeny obtained.

I have obtained my best resultsl with-a hollow cylinder` of magnesia mixed with about a satisfactwenty per cent. of oxid of thorium contain-I which we will assume is in the form of a hollow cylinder, Fig. 1, the coating becomes heated, because of its thinness and`conse quent resistance to the current. This in turn heats the body a., which when so heated is a conductor of electricity. The entire cylinder then speedily begins `to glow and emits a brilliant light.

My incandescent may be used as an illuminant in. the openair provided the metallic coating consists of a highly inoxidizable metal;` rbut if it contains any material quantity of osmiurn the incandescent should be 1 protected by a bulb that is exhausted or filled 5o with a neutral or-reducing gas.

Having thus described my inventionwhat I claim as new, and-desire to secure by Letters Patent, is- 1 .l yThe withindes'cribed. method of making Indeed, in any case it is sai"er', an'dv passage of thev electric curcandescent adapted to electric ligh ting, which' is so poor in luster as to give 'too thin a coating in one operation the operation of coating,

the metallic coating'b of the incandescent,

of those oxids of the earthy metals which become conductive and luminous at elevated. temperatures; second, applying to the sur- .face-.of` the body so formed a partial coatii; f

of a ceramic lustrous preparation of one or more ofthe highly-infusible metals of the platinum group; and lastly, burning saidceramic preparation in to reduce the same'to a metallic form and vcover the coated portion of said body with a supercial adherent filmA like deposit of such metal or metals.

l'2. VAs a new article of manufacture, an inconsists of a body composed of one or more,-

of those oxide of the earthy metals which become conductive and luminous at elevated teu'iperatures, provided with an initial heating device 'consisting of a film-like coherent and adherent partial coating of one or more of the highly-infusible metals of the platinum group producedby burning in a ceramic lus-- ter of the same. "v

3. As a new article ofmanufacture, an iu= candescent adapted to electric lighting, which consists of a body composed of one or more of those oxids of the earthy metals which become conductive and luminous at elevated temperatures, provided with an initial heating device consisting of a film-like coherent and adherent partial coating .of one or more o f the highly-infusible metals of the platinum group, as produced for example by burning in a'ceramic luster of thesaine.

4. As a new article of manufacture, an incandescent adapted to incandescent electric lighting, which consists of a hollow body composed of one or more of those oxids of the earthy metals which become conductive and luminous at elevated temperatures, provided with an initial heating device consisting of an interior adherent coating of one or more of the highly-infusible metals of the platinum group.y

Signed at Frankfortonethe-Main, in the Em pire of Germany, this lstday of June, A. D. 1899.

y GEORG ALEFELD.

Witnesses: t

l JEAN GRUND,

WILHELM Huss. 

